This invention relates to a table feed apparatus for reciprocating a table of grinder machines and the like.
For instance, in an internal grinder machine, there is mounted an oil-cylinder under the table thereof and by driving the oil-cylinder, the table is caused to rapidly transfer from a stand-by or non-working position to a working position (called a traverse movement) and by rotatably driving an eccentric cam assembly, which is provided at an end of a reciprocation axle protrudingly extending from the cylinder, a grinder wheel is caused to undergo a reciprocation movement (called an oscillation movement). In addition, in a conventional state of the art device, the eccentric cam assembly is comprised of a slide-ring mounted to undergo reciprocation, an eccentric cam slidably connected forwardly or backwardly of the transfer direction within the slide-ring, and a reciprocation axle for rotating the eccentric cam such that by rotatably driving the reciprocation axle, the eccentric cam exerts an eccentric movement and by slidably connecting to the inner side of the slide-ring, the table undergoes a reciprocation movement in response to the eccentric amount of the eccentric cam.
Further, the eccentric cam has a double ring configuration and an outer cam of which is connected to the inner wall of the slide-ring such that it constrains the traverse component force as well as possible and is adjustable only along the axial direction of the reciprocation axis. But, in the aforementioned table feed apparatus, an oil-cylinder is employed as a drive means for accomplishing the traverse movement such that it becomes impossible to exert a low speed feed to the workpiece. Thus the grinding versatility is very limited.
Further, with respect to the oscillation movement of the grinder table, the eccentric position of the eccentric cam is not so constant and thus the table is not accurately positioned. Accordingly, if the oscillation stroke needs to be changed, it is necessary to return the eccentric cam to the reference position and after that change the stroke thereof, hence the eccentric cam is troublesome in its stroke adjustment operation and its operation efficiency is very deteriorated.
Further, in a prior art table feed apparatus, when the operator needs to change the eccentric stroke of the eccentric cam, a control operation of the eccentric stroke is carried out in such a manner that an outer cam is caused to be free against an inner cam by unfastening an adjustment thread, and after the outer cam is rotated by the desired angle, the adjustment thread is again fastened. There are many times when this kind of manual operation becomes troublesome, for instance, when the oscillation operation of the table feed apparatus has a mechanical acceleration limit (vibration limit) such that if a long stroke is set, the oscillation cycle of the stroke or the rotation number of the eccentric cam is extremely restrained. Hence, in a practical operation, it is hard to cause an interlock therewith within the allowable range of the acceleration limit (vibration limit) under the consideration of the mutual relation between the oscillation stroke and the oscillation cycle. The manual operation is so difficult that it makes the stroke control operation more troublesome.